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Tips for Selecting or Designing a Membrane Switch

Saturday, 01 June 2013

Page 2 of 2

Is a back plate or bezel involved? Is
there a back plate or bezel to which the
membrane will be applied? If so, ask the
manufacturer to quote this. It makes your
sub-assembly more complete and easier
to install into your finished product.

Where will the switch be used?
Consider the environment in which the
membrane will be used so you can
design your membrane switch for maximum
reliability. For example, if it will be
used outdoors, you will want a graphic
material with UV protection. If it will be
used in an environment where ESD is
present, consider incorporating a shield
into the design.

Are there any industry-specific considerations
that apply to your design?
Some applications are simply harder on
switches than others. A control panel
for farm equipment may need to be
designed to IP67 standards to prevent
water ingress along with UV protected
material to prevent fading. Industrial
equipment used for manufacturing in a
clean room may need a shield to prevent
ESD from shorting out. Medical
equipment may need to be protected
with special antimicrobial material. For
example, APEM supplies Autotex AM, a
new hard-coated polyester film with
Microban® protection incorporated
into the textured hardcoat during the
manufacturing process.

What is the mating connector? You can
cut cost by using a standard 2.54mm
pitch female connector.

Are there specific ergonomic concerns
with the application? Consider embossing,
which allows the user to locate keys
easily. There are multiple types of
embossing, including pillow, rim, logo,
LED, and combination. Embossing can
be beneficial for low lighting environments
or for disabled users.

Is lighting required? Keypad can be
backlit, with a thin film electroluminescent
(EL) lamp, widely used for
medical equipment and robotic controls,
or light emitting diodes (LEDs),
used in medical equipment, power
supplies, generators, and hand-held
devices, provides visual indicators to
the user of actuation.

Do you need tactile feedback? In
many applications, it is important what
button is activated and when. From
medical hand-held devices to control
panels for industrial equipment, tactile
feedback from metal or polyester domes
is often required. Tactile feedback confirms
through touch and sound that the
switch was activated. If this is important
to your application, consider a stainless
steel dome, which can take high temperatures
and are extremely durable.
Polyester domes are rated to a maximum
temperature of 60°C (122°F).
Figure 2 shows a few possibilities for
domes that give tactile feedback.
Switches that do not require tactile feedback
tend to be less expensive and have
a simpler construction. They do not
require a dome or dome retainer.

How do I get a graphic design that is
aesthetically pleasing while not being
too expensive? You can use embossing,
multiple colors, graphic design, and
material finish to convey your company’s
message. To save on cost, minimizing
the number of colors, using standard
off-the-shelf connectors should be
incorporated into your design. Avoid
thin lines (less than 0.3mm) and serif
fonts, which can be costly to print. Keep
in mind that use of embossing and polycarbonate
material will increase costs.
Figure 3 provides some ideas on labels
and overlays.

Following the basic guidelines in this
article should simplify the job of selecting
or designing a membrane switch for
any application, and save you time and
money in the process.

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